Display device and manufacturing method thereof

ABSTRACT

A display device includes an array of light emitting cells. Each of the light emitting cells includes a first electrode, a second electrode, and an organic light emitting layer located between the first electrode and the second electrode. Banks are above the first electrode that partition the organic light emitting layer to define each of the light emitting cells. The light emitting cells include a peripheral light emitting cell that is located in a peripheral region of the array. The banks include first and second banks that each border the peripheral light emitting cell. The first bank is closer to a periphery of the array than the second bank. An inclination angle of an innermost sidewall of the first bank that is adjacent the peripheral light emitting cell is greater than an inclination angle of an outermost sidewall of the second bank that is adjacent the peripheral light emitting cell.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation application of PCT Application No.PCT/JP09/007,118 filed Dec. 22, 2009, designating the United States ofAmerica, the disclosure of which, including the specification, drawingsand claims, is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device and a manufacturingmethod thereof, and in particular to a display device provided with anorganic light emitting layer and a manufacturing method thereof.

2. Description of the Related Art

In recent years, progress has been made in the research and developmentof display devices that use the phenomenon of electroluminescenceoccurring in organic material. Each light emitting cell of such adisplay device is composed of an anode and a cathode with an organiclight emitting layer therebetween. When the display device is driven,light is produced when holes and electrons recombine within the organiclight emitting layer after injecting holes through the anode andinjecting electrons through the cathode.

Banks composed of insulating material partition the organic lightemitting layer of adjacent light emitting cells. The organic lightemitting layer is formed by dripping ink that includes organic lightemitting material into each region partitioned by the banks and dryingthe ink.

Maintaining a uniform film thickness in the organic light emitting layerformed in this way, however, is problematic.

To even out the film thickness of the organic light emitting layer,Patent Literature 1 for example recites an invention to provide aconvexity on the inner surface of the bank in order to control thepinning location of the ink. In other words, using the technologysuggested in Patent Literature 1, the pinning location when ink isdripped in one light emitting cell can be set to the convexity. To acertain degree, uniform film thickness can thus be guaranteed.

PATENT LITERATURES

-   Patent Literature 1: Japanese Patent Application Publication No.    2007-311235

SUMMARY OF INVENTION

It is considered difficult, however, to use the technology suggested inPatent Literature 1 over the entire panel of a display device (centralregion, peripheral region) to form a minute convexity on the innersurface of the bank to a high degree of precision in accordance witheach panel region. Therefore, it is not easy to maintain the organiclight emitting layer at a uniform film thickness over the entire panelof a display device (central region, peripheral region).

It is an object of the present invention to solve the above problems byproviding a display device, and a manufacturing method thereof, that hasa uniform film thickness in the organic light emitting layer in thelight emitting cells at the peripheral region of the panel and that hasan even luminance within the panel.

In order to solve the above problems, a display device according to anaspect of the present invention has the following structure.

A display device according to one aspect of the present inventioncomprises an array of a plurality of light emitting cells. The lightemitting cells are composed of a first electrode, a second electrode,and an organic light emitting layer located between the first electrodeand the second electrode. In the display device according to an aspectof the present invention, a plurality of banks is arranged above thefirst electrode so as to partition the organic light emitting layer intothe light emitting cells. The light emitting cells include a peripherallight emitting cell located in a peripheral region of the array(peripheral region of the panel), and the banks include a first bank anda second bank that border the peripheral light emitting cell, the firstbank bordering (i.e. being adjacent to) the peripheral light emittingcell on the side of the periphery of the array, and the second bankbordering (i.e. being adjacent to) the peripheral light emitting cell onthe side of the center of the array.

In the display device according to one aspect of the present invention,in the above structure, an inclination angle of a side wall facing theperipheral light emitting cell in the first bank is larger than aninclination angle of a side wall facing the peripheral light emittingcell in the second bank.

In the display device according to an aspect of the present invention,an inclination angle of a side wall facing a peripheral light emittingcell in a first bank (hereinafter referred to as “first side wall” forthe sake of simplicity) differs from an inclination angle of a side wallfacing a peripheral light emitting cell in a second bank (hereinafterreferred to as “second side wall” for the sake of simplicity).Therefore, when ink is dripped during manufacturing, a pinning locationof the ink on the first side wall becomes higher than a pinning locationof the ink on the second side wall.

The film thickness of the organic light emitting layer after dryingtends to establish an inverse relationship with the relative size of theinclination angle of the side wall of the bank. Therefore, the filmthickness at the location corresponding to the first side wall tends tobecome thinner than at the location corresponding to the second sidewall. Accordingly, in a display device according to an aspect of thepresent invention, even if a vapor stream is produced during drying,making the film thickness at the first side wall tend to become thicker,the reduction in film thickness due to making the inclination angle ofthe first side wall larger offsets this tendency. Therefore, it ispossible to make the film shape of the organic light emitting layer inthe peripheral light emitting cell uniform.

Accordingly, in the display device according to an aspect of the presentinvention, the film shape of the organic light emitting layer in thelight emitting cell located at the peripheral region of the panel can bemade uniform, and luminance can be made even.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a display device1 according to the Embodiment of the present invention.

FIG. 2 is a schematic cross-section diagram showing a light emittingcell 100 in a display panel 10.

FIG. 3 is a schematic plan view showing a bank 105 in the display panel10.

FIG. 4 is a schematic cross-section diagram showing the structure ofbanks 105 a-105 f in light emitting cells 100 a-100 c in the displaypanel 10.

FIG. 5A is a schematic cross-section diagram showing pinning locationswhen the taper angle of the bank side wall is small; FIG. 5B is aschematic cross-section diagram showing pinning locations when the taperangle of the bank side wall is large; FIG. 5C is a schematiccross-section diagram showing the condition of the organic lightemitting layer after drying when the taper angle of the bank side wallis small; and FIG. 5D is a schematic cross-section diagram showing thecondition of the organic light emitting layer after drying when thetaper angle of the bank side wall is large.

FIG. 6 summarizes the relationship between the inclination angle of thebank (taper angle) θ, the pinning height H, and the film thickness T ofthe organic light emitting layer.

FIG. 7 shows a distribution of film thickness of the organic lightemitting layer in samples 1-3.

FIG. 8 shows a distribution of film thickness of the organic lightemitting layer in samples 4 and 5.

FIGS. 9A, 9B, and 9C are schematic cross-section diagrams showing, inorder, the main processes in a manufacturing method of the display panel10.

FIGS. 10A, 10B, and 10C are schematic cross-section diagrams showing, inorder, the main processes in the manufacturing method of the displaypanel 10.

FIG. 11 is a schematic cross-section diagram showing the main processesin the manufacturing method of Modification 1.

FIGS. 12A and 12B are schematic cross-section diagrams showing, inorder, the main processes in the manufacturing method of Modification 2.

FIGS. 13A and 13B are schematic cross-section diagrams showing, inorder, the main processes in the manufacturing method of Modification 2.

FIG. 14A shows the relationship between the taper angle of a bank andexposure/developing, and FIG. 14B shows AFM graphs that indicate theshapes of banks.

FIG. 15 is an external perspective view showing an example of theappearance of a set that includes the display device 1.

FIG. 16 is a schematic plan view showing the structure of a bank 305provided in a display panel 30 according to a modification.

FIG. 17A is a schematic cross-section diagram showing the organic lightemitting layer in a display panel according to conventional technology,and FIG. 17B shows a uniformity distribution of film thickness of anorganic light emitting layer in each region of the display panel.

FIG. 18 is a schematic cross-section diagram showing a vaporconcentration distribution during a drying process when forming anorganic light emitting layer.

FIG. 19 is a schematic cross-section diagram illustrating the mechanismby which film shape becomes uneven during the drying process.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A display device according to one aspect of the present inventioncomprises an array of a plurality of light emitting cells. The lightemitting cells are composed of a first electrode, a second electrode,and an organic light emitting layer located between the first electrodeand the second electrode. In the display device according to an aspectof the present invention, a plurality of banks is arranged above thefirst electrode so as to partition the organic light emitting layer intothe light emitting cells. the light emitting cells include a peripherallight emitting cell located in a peripheral region of the array, and thebanks include a first bank and a second bank that border the peripherallight emitting cell, the first bank being closer to a periphery of thearray, and the second bank being closer to a center of the array.

In the display device according to one aspect of the present invention,in the above structure, an inclination angle of the first side wall islarger than an inclination angle of the second side wall.

In the display device according to one aspect of the present invention,since the inclination angle of the first side wall is larger than aninclination angle of the second side wall, when ink is dripped duringmanufacturing, a pinning location of the ink on the first side wallbecomes higher than a pinning location of the ink on the second sidewall. Specifically, the pinning location on the first wall with a largerinclination angle is higher than the pinning location on the second wallwith a smaller inclination angle. The film thickness of the organiclight emitting layer after drying has an inverse relationship with thesize of the inclination angle of the side wall of the bank. Therefore,the film thickness at the first side wall tends to be smaller than atthe second side wall.

This reduction in film thickness accompanying the change in pinninglocation by making the inclination angle of the first side wall largerthan the inclination angle of the second side wall offsets an increasein film thickness where solvent flows to minimize surface free energyduring drying. Therefore, the film shape of the entire peripheral lightemitting cell can be made even. Accordingly, in the display deviceaccording to an aspect of the present invention, the film thickness ofthe organic light emitting layer in a peripheral light emitting cell canbe made uniform and luminance made even by making the inclination angleof the first side wall larger than the inclination angle of the secondside wall in the peripheral light emitting cell.

The main characteristic of a display device according to an aspect ofthe present invention is that, by making the inclination angle of thefirst side wall larger than the inclination angle of the second sidewall, a pinning location of the organic light emitting layer in theperipheral light emitting cell becomes higher on the first side wallthan on the second side wall. Based on this characteristic, the displaydevice according to an aspect of the present invention has the aboveeffects.

In the display device according to one aspect of the present invention,in the above structure, the inclination angle of the first side wall maybe in a range between 35° and 40° inclusive, and the inclination angleof the second side wall may be in a range between 25° and 30° inclusive.By forming the first side wall and the second side wall with theseranges of inclination angles, the film thickness (film shape) of theorganic light emitting layer throughout each peripheral light emittingcell can be reliably made uniform.

In the display device according to one aspect of the present invention,in the above structure, a central light emitting cell located in thecentral region of the light emitting cell array may be furtherconsidered. In this case, the banks include a third bank and a fourthbank that border the central light emitting cell, the third bank beingcloser to the periphery of the array, and the fourth bank being closerto the center of the array. In the above structure, an inclination angleof a side wall facing the central light emitting cell in the third bank(hereinafter referred to as “third side wall” for the sake ofsimplicity) may be equivalent to an inclination angle of a side wallfacing the central light emitting cell in the fourth bank (hereinafterreferred to as “fourth side wall” for the sake of simplicity).

As shown in FIG. 17A, in the central region of the panel (central regionof the light emitting cell array), the film thickness of the organiclight emitting layer 906 in the central light emitting cell does notdiffer greatly at the left and right banks. Therefore, by making theinclination angles of the third side wall and the fourth side wallequivalent, the film thickness of the organic light emitting layerthroughout the central light emitting cell can be maintained uniform.

Note that the term “equivalent” above does not mean exact mathematicalequivalence, but rather takes factors such as tolerance whenmanufacturing the display device into account. Specifically, the term“equivalent” refers to making the inclination angles of the third sidewall and fourth side wall equivalent within the range permitted inpractice by the difference in luminous efficiency (uneven luminance)between the light emitting cells throughout the panel.

In the display device according to one aspect of the present invention,in the above structure, the inclination angle of the third side wall andthe inclination angle of the fourth side wall may be in a range between25° and 30° inclusive. By forming the third side wall and the fourthside wall with this range of inclination angle, the film thickness inthe organic light emitting layer in the central light emitting cells canbe made uniform throughout.

In the above structures, the “inclination angle” is an angle formed by aside wall of the bank and an upper surface of an underlayer on which thebank is provided (the underlayer corresponding to the first electrode,hole injection layer, hole transporting layer, or hole injectiontransporting layer).

A manufacturing method of a display device according to an aspect of thepresent invention is for manufacturing a display device comprising anarray of a plurality of light emitting cells, the manufacturing methodcomprising the following steps.

(Step 1) forming, above a substrate, a functional layer that includes aplurality of first electrodes.

(Step 2) layering photoresist material above the functional layer.

(Step 3) forming a plurality of openings corresponding to a plurality oflight emitting cells via mask exposure and patterning of the photoresistmaterial, and forming a plurality of banks that partition regionsbetween adjacent openings.

(Step 4) forming an organic light emitting layer by dripping ink thatincludes organic light emitting material through each of the openingsand drying the ink.

(Step 5) forming a plurality of second electrodes above the organiclight emitting layer.

Furthermore, in the manufacturing method of a display device accordingto one aspect of the present invention, the openings include aperipheral opening located in a peripheral region of the array, and thebanks include a first bank and a second bank that border a region of thearray corresponding to the peripheral opening, the first bank beingcloser to a periphery of the array, and the second bank being closer toa center of the array.

Also, in the third step, the first bank and the second bank are formedso that an inclination angle of a side wall facing the peripheralopening in the first bank (hereinafter referred to as “first side wall”for the sake of simplicity) is larger than an inclination angle of aside wall facing the peripheral opening in the second bank (hereinafterreferred to as “second side wall” for the sake of simplicity).

This manufacturing method can be used to manufacture a display device inwhich the first side wall has a larger inclination angle than the secondside wall. In a display device manufactured using this method, asdescribed above, a pinning location when ink is dripped duringmanufacturing into the peripheral opening is higher at the first sidewall than the second side wall. Due to the relationship between pinninglocation and film thickness described above, the film thickness of theorganic light emitting layer becomes uniform, and luminance is madeeven.

Accordingly, the manufacturing method of a display device according toan aspect of the present invention can be used to manufacture a displaydevice that has a uniform film thickness in the organic light emittinglayer in light emitting cells at the peripheral region of the panel(peripheral region of the light emitting cell array) and that has aneven luminance within the panel.

In the manufacturing method of a display device according to one aspectof the present invention, in the above structure, the openings include acentral opening located in a central region of the array, and the banksinclude a third bank and a fourth bank that border a region of the arraycorresponding to the central opening, the third bank being closer to theperiphery of the array, and the fourth bank being closer to the centerof the array. In the manufacturing method of a display device accordingto one aspect of the present invention, in the above structure, whenperforming the third step, the third bank and the fourth bank may beformed so that a side wall facing the central opening in the third bank(hereinafter referred to as “third side wall” for the sake ofsimplicity) and a side wall facing the central opening in the fourthbank (hereinafter referred to as “fourth side wall” for the sake ofsimplicity) have equivalent inclination angles.

By adopting this structure, the film thickness of the organic lightemitting layer at sections corresponding to the third side wall and thefourth side wall can be maintained uniform, making it possible toimprove uniformity of the organic light emitting layer at the centralopening.

Note that the meaning of “equivalent” is the same as above.

As described above, in the manufacturing method of a display deviceaccording to one aspect of the present invention, when forming theopenings and the banks, by forming the first bank and the second bank sothat the inclination angle of the first side wall is larger than theinclination angle of the second side wall, when forming the organiclight emitting layer, a pinning location of the ink dripped into theperipheral opening is set higher on the first side wall than on thesecond side wall, resulting in uniform film thickness in the organiclight emitting layer after drying. Accordingly, the manufacturing methodaccording to an aspect of the present invention can be used to reducevariation in the shape of the organic light emitting layer between lightemitting cells and to manufacture a display device that has an evenluminance.

In the manufacturing method of a display device according to one aspectof the present invention, in the above structure, when performing thethird step, the inclination angle of the first side wall may be madelarger than the inclination angle of the second side wall by varying,during exposure of the photoresist material, an exposure amount in asection corresponding to the first side wall and an exposure amount in asection corresponding to the second side wall. Specifically, by makingthe exposure amount in the section corresponding to the first side walllarger than the exposure amount in the section corresponding to thesecond side wall, the inclination angle of the first side wall can bemade larger than the inclination angle of the second side wall.

In the manufacturing method of a display device according to one aspectof the present invention, in the above structure, when performing thethird step, the inclination angle of the first side wall may be madelarger than the inclination angle of the second side wall by using,during exposure of the photoresist material, a mask in which a degree oftransparency in a section corresponding to the first side wall and adegree of transparency in a section corresponding to the second sidewall differ. Accordingly, the inclination angle of the first side wallbecomes larger than the inclination angle of the second side wall,making it possible to manufacture a display device with little varietyin luminance across the panel.

Specifically, the degree of transparency in the mask may be larger inthe section corresponding to the first side wall than in the sectioncorresponding to the second side wall.

In the manufacturing method of a display device according to one aspectof the present invention, when performing the third step, after exposingand developing the photoresist material in a section corresponding tothe first side wall and a section corresponding to the second side wall,the photoresist material in one of the sections may be additionallyexposed. This method may also be adopted to form the first bank and thesecond bank so that the inclination angle of the first side wall islarger than the inclination angle of the second side wall. Specifically,when performing the third step, the section corresponding to the firstside wall may be additionally exposed. In this way, the inclinationangle of the first side wall can be made larger than the inclinationangle of the second side wall.

Embodiment

The following describes an example of an embodiment of the presentinvention with reference to the drawings.

Note that the following Embodiment is simply an example to clearlyillustrate a structure of the present invention and the effects andadvantages thereof. The present invention is in no way limited to thefollowing Embodiment except in its essential characteristic elements.

(Process by which the Embodiment According to the Present Invention wasAchieved)

As a result of intense study, the inventor of the present inventiondiscovered the following with regard to the organic light emittingdisplay device recited in the Background Art.

Normally, as shown in FIG. 17A, an organic light emitting layer 906 a,906 c is formed between banks 905 provided above a substrate 901.

The inventor determined that in this case, as shown in FIG. 17B, theorganic light emitting layer 906 c at the light emitting cell at theperipheral region of the panel tends to have a less uniform filmthickness than the organic light emitting layer 906 a at the lightemitting cell in the central region of the panel (as shown by the lineswith alternate long and two short dashes D₁ and D₂ in FIG. 17B).Specifically, in the light emitting cell located at the peripheralregion of the panel, the surface of the organic light emitting layerbecomes higher as it approaches the outer periphery of the panel. Notethat, in FIG. 17B, the horizontal axis indicates distance from the outerperiphery, and the vertical axis indicates the degree of deviance of thefilm thickness.

After repeated examination of the above phenomenon, the inventordetermined that reduction in uniformity of film thickness in the organiclight emitting layer causes a non-uniform vapor concentrationdistribution during ink drying, as described below. Specifically, asshown in FIG. 18, the vapor concentration near the light emitting cells900 b and 900 c located at the peripheral region of the panel is lowerthan the vapor concentration near the light emitting cell 900 a locatedat the central region of the panel. This unevenness in the vaporconcentration distribution causes the evaporation rate of solvent fromink dripped in the light emitting cells 900 b and 900 c in theperipheral region of the panel to become non-uniform (see the lines withalternate long and two short dashes in FIG. 18).

By contrast, the evaporation rate of solvent from ink dripped in thelight emitting cell 900 a at the central region of the panel is roughlyuniform.

However, as shown in FIG. 19B, solvent in the ink 9061 c flows duringdrying as shown by the solid arrow. This is because solvent flows tocompensate for solvent that has evaporated (i.e. flows to minimizesurface free energy), and along with the flow of the solvent, the solute(organic light emitting material) also flows. Therefore, as shown inFIG. 19C, in a light emitting cell at the peripheral region of thepanel, an organic light emitting layer 906 c with a surface profile L2that swells up towards the exterior forms.

The inventor therefore deduced that, in an organic light emittingdisplay device, uniformity of film thickness of the organic lightemitting layer decreases due to non-uniformity of vapor concentrationdistribution during ink drying in the peripheral region and centralregion of a panel.

The inventor also discovered technology to vary, within the panel, thepinning location of ink on a bank side wall by varying the inclinationangle of the bank side wall, which improves uniformity of film thicknessin the organic light emitting layer.

1. Configuration of Display Device 1

The overall structure of the display device 1 according to the presentEmbodiment is described with reference to FIG. 1.

As shown in FIG. 1, the display device 1 is composed of a display panelunit 10 and a drive control unit 20 connected to the display panel unit10. The display panel unit 10 is an organic EL panel that uses thephenomenon of electroluminescence occurring in organic material and iscomposed of an array of a plurality of organic EL elements.

The drive control unit 20 is composed of four drive circuits 21-24 and acontrol circuit 25.

Note that in an actual display device 1, the placement of the drivecontrol unit 20 with respect to the display panel unit 10 is not limitedin this way.

2. Structure of Display Panel 10

The structure of the display panel 10 is described with reference toFIG. 2. Note that, as an example, the display panel 10 in the presentEmbodiment is a top emission type organic EL panel composed of aplurality of light emitting cells 100 that are each provided with anorganic light emitting layer having a luminescent color of either red(R), green (G), or blue (B) arranged in a matrix. FIG. 2 depicts onelight emitting cell 100.

As shown in FIG. 2, in the display panel 10, an anode 102 is formedabove a TFT substrate (hereinafter simply referred to as a “substrate”)101, and an electrode coating layer 103 and hole injection transportinglayer 104 are layered above the anode 102 in this order. Note that theanode 102 and electrode coating layer 103 are formed separately for eachlight emitting cell 100.

The hole injection transporting layer 104 is formed to coat theelectrode coating layer 103, and above the hole injection transportinglayer 104, banks 105 formed from insulating material are established topartition each light emitting cell 100. An organic light emitting layer106 is formed in the region in each light emitting cell 100 partitionedby the banks 105, and an electron injection layer 107, cathode 108, andpassivation layer 109 are layered above the organic light emitting layer106 in this order.

a) Substrate 101

The substrate 101 is formed with a base of an insulating material suchas alkalifree glass, soda glass, nonfluorescent glass, phosphate glass,borate glass, quartz, acrylic resin, styrenic resin, polycarbonateresin, epoxy resin, polyethylene, polyester, silicon resin, alumina,etc.

b) Anode 102

The anode 102 is composed of a single layer or of a laminate of aplurality of layers of a conductive material, such as Ag (silver), APC(alloy of silver, palladium, and copper), ARA (alloy of silver,rubidium, and gold), MoCr (alloy of molybdenum and chromium), NiCr(alloy of nickel and chromium), etc. Note that in the case of a topemission type panel such as in the present Embodiment, it is preferablethat the anode 102 be formed with highly reflective material.

c) Electrode Coating Layer 103

The electrode coating layer 103 is formed, for example, using indium tinoxide (ITO) and covers a surface located above the anode 102 along the Zaxis.

d) Hole Injection Transporting Layer 104

The hole injection transporting layer 104 is a layer of an oxide such assilver (Ag), molybdenum (Mo), chromium (Cr), vanadium (V), tungsten (W),nickel (Ni), iridium (Ir), etc. A hole injection transporting layer 104formed from such a metal oxide has the function of assisting with holegeneration and of injecting and transporting holes stably into theorganic light emitting layer 106. The hole injection transporting layer104 has a high work function.

When the hole injection transporting layer 104 is formed from an oxideof a transition metal, a plurality of levels can be occupied since thereare a plurality of oxidation numbers. This makes hole injection easy andallows for reduction of driving voltage.

Note that in addition to forming the hole injection transporting layer104 with the above-described metal oxides, PEDOT (an amalgam ofpolythiophene and polystyrene sulfonic acid) or the like may also beused.

e) Banks 105

The banks 105 are formed with an organic material such as resin and haveinsulating properties. Examples of the organic material used to form thebanks 105 include acrylic resin, polyimide resin, styrenic resin,polycarbonate resin, novolac-type phenolic resin, etc. It is alsopreferable that the banks 105 have organic solvent resistance.

Furthermore, since the banks 105 are etched and baked when formed, it ispreferable that the banks be formed from highly resistant material thatwill not change in shape or quality during the etching and bakingprocesses. To provide the banks with liquid repellency, the side wallscan be fluoridated.

Note that as the insulating material used in forming the banks 105, anyliquid repellent material with a resistivity of 10⁵Ω·cm can be used,starting with the above materials. Using a material with a resistivityof less than 10⁵Ω·cm leads to production of leak current between theanode 102 and the cathode 108, or between adjacent light emitting cells100, which causes a variety of problems such as increased powerconsumption.

Furthermore, if a hydrophilic material is used to form the banks 105,the difference in affinity/liquid repellency between the side wall ofthe banks 105 and the surface of the hole injection transporting layer104 becomes small, and it thus becomes difficult to selectively maintainthe ink, which includes an organic substance for forming the organiclight emitting layer 106, at the opening of the banks 105.

The structure of the banks 105 need not be a single layer as shown inFIG. 2, but may adopt a two or more layered structure. In such a case,the above materials may be combined for each layer, or layers mayalternate between non-organic and organic material.

f) Organic Light Emitting Layer 106

The organic light emitting layer 106 has a function of emitting lightwhen an excitation state is produced by the recombination of holesinjected through the anode 102 with electrons injected through thecathode 108. The material used to form the organic light emitting layer106 needs to be a light emitting organic material, a film of which canbe formed by wet printing.

Specifically, it is preferable that the organic light emitting layer 106be formed from a fluorescent material such as an oxinoid compound,perylene compound, coumarin compound, azacoumarin compound, oxazolecompound, oxadiazole compound, perinone compound, pyrrolo-pyrrolecompound, naphthalene compound, anthracene compound, fluorene compound,fluoranthene compound, tetracene compound, pyrene compound, coronenecompound, quinolone compound and azaquinolone compound, pyrazolinederivative and pyrazolone derivative, rhodamine compound, chrysenecompound, phenanthrene compound, cyclopentadiene compound, stilbenecompound, diphenylquinone compound, styryl compound, butadiene compound,dicyanomethylene pyran compound, dicyanomethylene thiopyran compound,fluorescein compound, pyrylium compound, thiapyrylium compound,selenapyrylium compound, telluropyrylium compound, aromatic aldadienecompound, oligophenylene compound, thioxanthene compound, anthracenecompound, cyanine compound, acridine compound, metal complex of a8-hydroxyquinoline compound, metal complex of a 2-bipyridine compound,complex of a Schiff base and a group three metal, metal complex ofoxine, rare earth metal complex, etc., as recited in Japanese PatentApplication Publication No. H5-163488.

g) Electron Injection Layer 107

The electron injection layer 107 has the function of transportingelectrons injected through the cathode 108 to the organic light emittinglayer 106 and is preferably formed, for example, of barium,phthalocyanine, lithium fluoride, or a combination thereof.

h) Cathode 108

The cathode 108 is formed, for example, of ITO, indium zinc oxide (IZO),etc. In the case of the top-emission type display panel 10, it ispreferable that the passivation layer 109 be formed with a transparentmaterial. It is preferable that the degree of transparency be 80% orgreater.

The material used to form the cathode 108 may, in addition to the abovematerials, be for example an alkali metal or alkali earth metal, or alaminate structure having, in the following order, a layer that includesa halide of an alkali metal or alkali earth metal and a layer thatincludes silver. The layer that includes silver may be formed withsilver alone, or with a silver alloy. Also, in order to increase lighttakeoff efficiency, a highly transparent refraction index adjustmentlayer may be provided above the layer that includes silver.

i) Passivation Layer 109

The passivation layer 109 has the function of controlling the organiclight emitting layer 106 or other layers from being exposed to water orair and is formed, for example, with silicon nitride (SiN), siliconoxynitride (SiON) etc. In the case of the top-emission type displaypanel 10, it is preferable that the passivation layer 109 be formed witha transparent material.

3. Structure of Banks 105

As shown in FIG. 3, the banks 105 arranged in a line are adopted as oneexample in the display panel 10 according to the present Embodiment.Specifically, the banks 105 each extend along the Y axis and partitionadjacent light emitting cells 100 along the X axis. The light emittingcells 100 are formed so that adjacent regions partitioned by banks 105have a different luminescent color.

4. Structure of Banks 105 in Each Region

As shown in FIG. 4, a light emitting cell 100 a located in the centralregion, and light emitting cells 100 b and 100 c located at theperipheral region (the light emitting cells located at either peripheryof a row of light emitting cells) have been extracted from the displaypanel 10. Banks 105 a-105 f are provided on either side of these lightemitting cells 100 a, 100 b, and 100 c.

Side walls 105 aa and 105 ba, respectively facing the light emittingcell 100 a in the banks 105 a and 105 b, respectively form angles θa andθb with a surface 104 a of the underlayer, i.e. the hole injectiontransporting layer 104.

On the other hand, side walls 105 ca-105 fa facing the light emittingcells 100 b and 100 c in the banks 105 c-105 f respectively form anglesθc-θf with the surface 104 a of the hole injection transporting layer104. These angles θaθf satisfy the relationships in the followingexpressions.

θf>θe  [Expression 1]

θc>θd  [Expression 2]

θa=θb=θd=θe  [Expression 3]

Note that in the present Embodiment, the angles θa, θb, θd, and θe arewithin a range of 25° and 30° inclusive, and the angles θc and θf arewithin a range of 35° and 40° inclusive.

5. Relationship Between Inclination Angle θ of Side Wall of Banks 105and Film Thickness of Organic Light Emitting Layer 106

The relationship between the inclination angle θ of the side wall of thebanks 105 and the film thickness of the organic light emitting layer 106is described with reference to FIGS. 5 and 6. Note that FIG. 5 is aschematic rendering of the structure of a light emitting cell.

As shown in FIG. 5A, the inclination angle of the side wall of bank 105x (the angle between the side wall and the surface of the hole injectiontransporting layer 104) is θx, and as shown in FIG. 5B, the inclinationangle of the side wall of bank 105 y (the angle between the side walland the surface of the hole injection transporting layer 104) is θy. θxand θy satisfy the following relationship.

θy>θx  [Expression 4]

When ink 1060 x and ink 1060 y, which include organic light emittingmaterial, are dripped into the opening partitioned by the banks 105 xand 105 y, the pinning locations Px and Py respectively have heights Hxand Hy that satisfy the following relationship.

Hy>Hx  [Expression 5]

As shown in FIG. 5C, after drying the ink 1060 x, the height Hx of thepinning location Px is relatively low, which causes the organic lightemitting layer 106 x to swell at the central portion of the lightemitting cell to a film thickness of Tx.

On the other hand, as shown in FIG. 5D, after drying the ink 1060 y, theheight Hy of the pinning location Py is relatively high, which causesthe organic light emitting layer 106 y to sag at the central portion ofthe light emitting cell to a film thickness of Ty.

The thicknesses Tx and Ty satisfy the following relationship.

Tx>Ty  [Expression 6]

FIG. 6 summarizes the above relationships. As shown in FIG. 6, as theinclination angle (taper angle) θ of the bank 105 grows smaller, thepinning height H lowers, and as a result, the film thickness T of theorganic light emitting layer 106 becomes thicker. Conversely, as theinclination angle (taper angle) θ of the bank 105 grows larger, thepinning height H becomes higher, and as a result, the film thickness Tof the organic light emitting layer 106 becomes thinner.

Based on the above factors, five samples were created and evaluated.FIGS. 7 and 8 show the results.

As shown in FIGS. 7 and 8, as compared to the distribution of filmthickness of sample 2, the pinning location is higher in samples 3 and4, which have a larger taper angle. Note that in FIGS. 7 and 8, thehorizontal axis represents the horizontal direction, and the verticalaxis represents the direction of height.

In sample 5, however, in which the bank has a taper angle (inclinationangle) of 50°, the film thickness is less uniform than in sample 2.

6. Manufacturing Method of Display Panel 10

The following describes the characteristic steps of the manufacturingmethod of the display panel 10 according to the present Embodiment withreference to FIGS. 9 and 10. Note that with regard to the manufacturingprocesses that are omitted in the following description, any of thevariety of processes suggested by conventional technology may be used.

First, as shown in FIG. 9A, above the substrate 101 in the direction ofthe Z axis, anodes 102 and electrode coating layers 103 are layered inthis order in regions in which each light emitting cell 100 a, 100 c, .. . is to be formed. A hole injection transporting layer 104 is thenlayered on top so as to cover the entire surface. The anodes 102 areformed, for example, by first forming a thin Ag film via the sputteringmethod or vacuum deposition method and then patterning the thin Ag filmvia photolithography.

The electrode coating layers 103 are formed, for example, by forming athin ITO film on the surface of the anodes 102 using a method such asthe sputtering method and then patterning the thin ITO film via a methodsuch as photolithography. To form the hole injection transporting layer104, first a metal film is formed on the surface of the substrate 101,including the surface of the electrode coating layer 103, via a methodsuch as the sputtering method. Subsequently, the metal film becomesoxidized, forming the hole injection transporting layer 104.

Next, as shown in FIG. 9B, the spin coat method, for example, is used toform a bank material layer 1050 so as to cover the top of the holeinjection transporting layer 104. Photoresist material is used to formthe bank material layer 1050. Specifically, as described above, anorganic material having insulating properties such as acrylic resin,polyimide resin, novolac-type phenolic resin, etc. can be used.

Next, as shown in FIG. 9C, a mask 501 is placed above the bank materiallayer 1050, the mask 501 having openings 501 a and 501 c at thelocations for forming the banks. Light is exposed through the openings501 a and 501 c in the mask 501.

Note that, as shown in FIG. 9C, in the region corresponding to the lightemitting cell 100 a located in the central region, a width Wa of theopenings 501 a in the mask 501 is defined by points Pa1 and Pa2 at thebottom edges of side walls of the banks 105 a and 105 b (see FIG. 4)that are being formed. On the other hand, in the region corresponding tothe light emitting cell 100 c located at the peripheral region, a widthWc1 of the openings 501 a in the mask is defined by a point Pc1 at theupper edge of a side wall and a point Pc2 at the foot of a side wall ofthe banks 105 e and 105 f (see FIG. 4) that are being formed.

Next, as shown in FIG. 10A, above the bank material layer 1050, a mask502 is placed, the mask 502 having openings 502 c at the locationscorresponding to the side wall 105 fa of the bank 105 f (see FIG. 4),etc. Light is exposed for the second time through the openings 502 c inthe mask 502.

Note that a width Wc2 of the openings 502 c in the mask 502 is definedby a point Pc3 at the bottom edge and the point Pc1 at the upper edge ofa side wall of the banks 105 e and 105 f that are being formed.

Next, as shown in FIG. 10B, the banks 105 a, 105 c, 105 e, and 105 f areformed by development and baking. The side wall 105 fa of the bank 105f, as described above, has a larger inclination angle than the sidewalls 105 aa and 105 ba of the banks 105 a and 105 b, and the side wall105 ea of the bank 105 e has an equivalent inclination angle to the sidewalls 105 aa and 105 ba of the banks 105 a and 105 b.

Subsequently, as shown in FIG. 10C, ink that includes an organic lightemitting material is dripped into the openings partitioned by the banks105 a, 105 b, 105 e, 105 f, . . . by the inkjet method or other method.By drying the ink, the organic light emitting layer 106 a and 106 cforms.

Note that, although omitted from the drawings, the display panel 10 isformed by layering, in order, the electron injection layer 107, cathode108, passivation layer 109, etc.

7. Advantageous Effects

As shown in FIG. 4, in the display panel 10 in the display device 1according to the present invention, the inclination angles θc and θf theside walls 105 ca and 105 fa respectively facing the light emittingcells 100 b and 100 c in the banks 105 c and 105 f and located closer tothe periphery of the panel are set larger than the inclination angles θdand θe of the side walls 105 da and 105 ea respectively facing the samelight emitting cells 100 b and 100 c in the banks 105 d and 105 e andlocated closer to the center of the panel (see Expressions 1 and 2above). Accordingly, in the light emitting cells 100 b and 100 c locatedin the peripheral region of the panel, when ink is dripped duringmanufacturing, a pinning location of the ink on the side walls 105 daand 105 ea of the banks 105 d and 105 e located closer to the center ofthe panel becomes higher than a pinning location of the ink on the sidewalls 105 ca and 105 fa of the banks 105 c and 105 f located closer tothe periphery of the panel. Therefore, establishing the aboverelationship between the inclination angles θc-θf in the side walls 105ca-105 fa of the banks 105 c-105 f has the effect of controlling thetendency of the film thickness of the organic light emitting layer 106,at an edge thereof closer to the outer periphery of the panel, to becomethicker in the light emitting cells 100 b and 100 c, which are locatedat the peripheral region of the panel, due to vapor concentrationdistribution during ink drying. The film thickness in the organic lightemitting layer 106 in the light emitting cells 100 b and 100 c locatedat the peripheral region of the panel can thus be made uniformthroughout.

Also, the inclination angles θd and θe of the side walls 105 da and 105ea in the banks 105 d and 105 e are equivalent to the inclination anglesθa and θb of the side walls 105 aa and 105 ba in the banks 105 a and 105b. Accordingly, the film thickness of the organic light emitting layer106 in each section becomes equivalent throughout the panel.

Therefore, in the display panel 10, the film thickness of the organiclight emitting layer 106 after drying is uniform between light emittingcells 100 a, 100 b, 100 c, . . . , which has the advantageous effect ofeven luminance.

Note that the manufacturing method of the display device 1 according tothe present invention as described with reference to FIGS. 9 and 10 canbe used to manufacture a display device 1 having these advantageouseffects.

Note that, as above, the term “equivalent” does not mean exactmathematical equivalence, but rather takes factors such as tolerancewhen manufacturing the display device into account. Specifically, theterm “equivalent” refers to making the inclination angles equivalentwithin the range permitted in practice by the difference in luminousefficiency (uneven luminance) between the light emitting cells 100 a,100 b, 100 c, . . . in the central region and peripheral region of thepanel.

[Modification 1]

Next, with reference to FIG. 11, Modification 1 of the manufacturingmethod of the display device 1 is described. FIG. 11 shows processescorresponding to the processes shown from FIG. 9C to FIG. 10A.

As shown in FIG. 11, after layering a bank material layer 1050 on top ofthe hole injection transporting layer 104, a mask 503 is placed abovethe bank material layer 1050. The mask 503 has optical transmissionsections 503 a, 503 c 1, 503 c 2, . . . . The optical transmissionsections 503 a, 503 c 1, 503 c 2, . . . are provided in correspondenceto the locations where the banks 105 a-105 f, . . . are to be formed.

In the manufacturing method of the display device 1 according toModification 1, the width Wa of the optical transmission sections 503 a,in the region corresponding to the light emitting cell 100 a, is definedby the points Pa1 and Pa2 at the bottom edges of the banks 105 a and 105b (see FIG. 4) that are being formed.

On the other hand, the width Wc2 of the optical transmission sections503 c 1, in the region corresponding to the light emitting cell 100 c,is defined by the point Pc2 at the bottom edge and the point Pc1 at theupper edge of the banks 105 e and 105 f (see FIG. 4) that are beingformed. The optical transmission section 503 c 2 is defined by thepoints Pc3 and Pc1 at the bottom edges of the banks 105 e and 105 f (seeFIG. 4) that are being formed.

The mask 503 is formed using a half-tone or other mask, and the degreeof transparency of the optical transmission sections 503 a and 503 c 1differs from that of the optical transmission sections 503 c 2.Specifically, the degree of transparency of the optical transmissionsections 503 c 2 is larger than the degree of transparency of theoptical transmission sections 503 a and 503 c 1.

The mask 503 with the above-described structure is put in place, andafter exposure and development, the banks 105 a, 105 b, 105 e, and 105 fare formed as shown in FIG. 10B by baking. In other words, at thelocation exposed to light via the optical transmission section 503 c 2,which has a larger degree of transparency, the side wall has a largerinclination angle than at the locations exposed to light via the opticaltransmission sections 503 a and 503 c 1, as in the relationshipsindicated in Expressions 1 and 2.

Subsequent processes are the same as the above Embodiment.

With regards to the above relationships for the amount of exposure, notethat depending on a variety of conditions, such as the type ofphotoresist material, which is the structural material for the banks105, the direction of the inequalities may be reversed.

The display device 1 can be manufactured with this type of manufacturingmethod.

[Modification 2]

Next, with reference to FIGS. 12 and 13, Modification 2 of themanufacturing method of the display device 1 is described. FIGS. 12 and13 show processes corresponding to the processes shown from FIG. 9C toFIG. 10B.

As shown in FIG. 12A, after layering a bank material layer 1050 on topof the hole injection transporting layer 104, a mask 504 is placed abovethe bank material layer 1050. The mask 504 has openings 504 a, 504 c, .. . corresponding to the sections at which banks 105 are to be formed.

The openings 504 a, provided at locations where the banks 105 a and 105b (see FIG. 4) are to be formed in correspondence with the lightemitting cell 100 a, are formed to have the same width as the openings501 a in the mask 501 used in the manufacturing method of the aboveEmbodiment. On the other hand, a width Wc3 of the openings 504 c,provided at locations where the banks 105 e and 105 f (see FIG. 4) areto be formed in correspondence with the light emitting cell 100 c, isset to be larger than the width defined by the points Pc2 and Pc3 at thelower edges of the banks 105 e and 105 f, as shown by the sectionsurrounded by lines with alternate long and two short dashes in FIG.12A. Specifically, the width is made larger at the sections where theinclination angle is to be greater.

The mask 504 shown in FIG. 12A is put in place, and exposure anddevelopment take place for the first time. As shown in FIG. 12B, bankmaterial layers 1051 a, 1051 b, 1051 e, and 1051 f remain in thelocations corresponding to the openings 504 a and 504 c.

Note that, as shown in FIG. 12B, the inclination angles of each sidewall in the bank material layers 1051 a, 1051 b, 1051 e, and 1051 f areuniform after the first exposure and development. In Modification 2,baking does not take place at this point.

As shown in FIG. 13A, a mask 505 is placed above the bank materiallayers 1051 a, 1051 b, 1051 e, and 1051 f that have formed. Among thelocations in the mask 505 corresponding to the side walls of the banks105 a-105 f, . . . that are being formed, openings 505 c are providedonly at the locations where the inclination angle is to be made larger.

With the mask 505 set in place, exposure and development takes place forthe second time, and the banks 105 a, 105 b, 105 e, and 105 f shown inFIG. 13B are formed by baking.

Subsequently, the display device 1 can be manufactured by performing thesame processes as in the above Embodiment and Modification.

[Verification of Manufacturing Method]

Using a concrete example, the shape of the banks after formation wasverified for the manufacturing method according to the above Embodimentand Modifications 1 and 2. The results are described with reference toFIG. 14.

As shown in FIG. 14, as the exposure amount increases, the inclinationangle of the side wall of the bank that is formed becomes larger.Specifically, when exposure and development take place with an exposureamount of 200 mJ, the inclination angle of the side wall of the bankthat is formed is 23°, whereas when exposure and development take placewith an exposure amount of 300 mJ, the inclination angle of the sidewall of the bank that is formed is 38°. This result was also shown bythe Atomic Force Microscope (AFM) shown in FIG. 14B.

Furthermore, as shown in FIGS. 14A and 14B, after light exposure anddevelopment take place for the first time with an exposure amount of 200mJ and subsequently for the second time with an exposure amount of 100mJ, the inclination angle of the side wall of the bank that is formed is50°. This corresponds to the manufacturing method according toModification 2 and is considered to be effective for creating a largeinclination angle of the bank side wall.

Note that in FIG. 14B, the horizontal axis represents the horizontaldirection, and the vertical axis represents the direction of height.

[Other Considerations]

In the above Embodiment and Modifications 1 and 2, structures wereadopted by way of example in order to clearly illustrate a structure ofthe present invention and the effects and advantages thereof. Except forits essential elements, the present invention is not limited to theabove structures. For example, in the above Embodiment, as shown in FIG.2, a structure was adopted by way of example in which anodes 102 arelocated below the organic light emitting layer 106 in the direction ofthe Z axis. The present invention is not limited, however, to thisstructure; a structure may be adopted in which cathodes 108 are locatedbelow the organic light emitting layer 106 in the direction of the Zaxis.

In the case in which cathodes 108 are located below the organic lightemitting layer 106 in the direction of the Z axis, since the panel is atop-emission structure, a structure is adopted in which the cathodes 108are a reflecting electrode layer, above which the electrode coatinglayer 103 is formed.

In the above Embodiment and Modifications, a specific example of theappearance of the display device 1 is not shown. The display device 1may be part of a system as shown, for example, in FIG. 15. Note that anorganic EL display device does not require a backlight, as does a liquidcrystal display device, and is therefore suitable for producing athinner display, a superior characteristic from the perspective ofsystem design.

Also, in the above Embodiment and Modifications 1 and 2, a so-calledline bank structure is adopted as the shape of the banks 105, as shownin FIG. 3. However, as shown in FIG. 16, a “pixel bank” 305 may beadopted in the structure of a display panel 30, the pixel bank 305 beingformed by bank elements 305 a that extend in the direction of the Y axisand bank elements 305 b that extend in the direction of the X axis.

As shown in FIG. 16, when using the pixel bank 305, the sameadvantageous effects as above can be achieved by enlarging theinclination angle of the side walls on each side in the directions ofthe X axis and the Y axis of the light emitting cell 300 at theperipheral region of the panel. Specifically, in the light emitting cellthat is located at the corner of the peripheral region of the panel andhas side walls indicated by arrows B1, B2, B3, and B4, the inclinationangle of the side walls indicated by the arrows B1 and B3 should be madelarger than the inclination angle of the side walls indicated by thearrows B2 and B4.

In the above Embodiment and Modifications 1 and 2, the inclination angleof the side walls of the banks at the peripheral region of the panel aremade larger than the inclination angle of the side walls of the banks atthe central region of the panel. However, this relationship may bevaried according to the flow of vapor (vapor concentration) during thedrying process in the formation of the organic light emitting layer atthe time of manufacturing. For example, if the flow of vapor duringdrying of the ink is from the outer periphery of the panel towards thecentral region of the panel due to some factor such as the structure ofthe drying device, then the inclination angle of the bank side walls maybe made larger at locations where the film thickness of the organiclight emitting layer becomes thicker. The film thickness of the organiclight emitting layer can thus be made uniform, which has theadvantageous effect of making luminance more even throughout the panel.

While no distinction is made between the luminescent colors (red, green,blue) of the light emitting cells in the above Embodiment and inModifications 1 and 2, the characteristics of the ink included in theorganic light emitting material change according to luminescent color.The inclination angle of the corresponding bank side wall can bespecified in accordance with the ink characteristics of each luminescentcolor.

The region in which the inclination angle of the bank side wall isincreased may be varied according to the manufacturing process, panelsize, etc. It is considered preferable, however, for this region toencompass light emitting cells located, for example, in a range of 0.5%to a few percentage points (e.g. 1%) of the peripheral region of thepanel. This range is based on a consideration of variety in filmthickness of the organic light emitting layer in a display deviceaccording to conventional technology.

INDUSTRIAL APPLICABILITY

The present invention is useful for achieving a display device thatexhibits even luminance and is capable of high image quality.

1. A display device, comprising: an array of a plurality of lightemitting cells, each of the plurality of light emitting cells includinga first electrode, a second electrode, and an organic light emittinglayer located between the first electrode and the second electrode; anda plurality of banks above the first electrode that partition theorganic light emitting layer to define each of the plurality of lightemitting cells, wherein the plurality of light emitting cells includes aperipheral light emitting cell that is located in a peripheral region ofthe array, the plurality of banks includes a first bank and a secondbank that each border the peripheral light emitting cell, the first bankbeing closer to a periphery of the array than the second bank, thesecond bank being closer to a center of the array than the first bank,and an inclination angle of an innermost sidewall of the first bank thatis adjacent the peripheral light emitting cell is greater than aninclination angle of an outermost sidewall of the second bank that isadjacent the peripheral light emitting cell.
 2. The display device ofclaim 1, wherein a first pinning location of the organic light emittinglayer in the peripheral light emitting cell on the innermost sidewall ofthe first bank is higher than a second pinning location of the organiclight emitting layer in the peripheral light emitting cell on theoutermost sidewall of the second bank as a result of the inclinationangle of the innermost sidewall of the first bank being greater than theinclination angle of the outermost sidewall of the second bank.
 3. Thedisplay device of claim 1, wherein the inclination angle of theinnermost sidewall of the first bank is at least approximately 35° andat most approximately 40°, and the inclination angle of the outermostsidewall of the second bank is at least approximately 25° and at mostapproximately 30°.
 4. The display device of claim 1, wherein theplurality of light emitting cells includes a central light emitting cellthat is located in a central region of the array, the plurality of banksincludes a third bank and a fourth bank that each border the centrallight emitting cell, the third bank being closer to the periphery of thearray than the fourth bank, and the fourth bank being closer to thecenter of the array than the third bank, and an inclination angle of aninnermost sidewall of the third bank that is adjacent the central lightemitting cell is approximately equal to an inclination angle of anoutermost sidewall of the fourth bank that is adjacent the central lightemitting cell.
 5. The display device of claim 4, wherein the inclinationangle of the innermost sidewall of the third bank and the inclinationangle of the outermost sidewall of the fourth bank are at leastapproximately 25° and at most approximately 35°.
 6. The display deviceof claim 1, wherein the inclination angle of each of the innermostsidewall of the first bank and the outermost sidewall of the second bankis an angle formed by a corresponding one of the innermost sidewall offirst bank and the outermost sidewall of the second bank and anunderlayer on which each of the first bank and the second bank areprovided.
 7. A manufacturing method of a display device that includes anarray of a plurality of light emitting cells, the manufacturing methodcomprising: forming, above a substrate, a functional layer that includesa plurality of first electrodes; layering photoresist material above thefunctional layer; forming a plurality of openings that correspond to theplurality of light emitting cells and a plurality of banks thatpartition the plurality of openings via mask exposure and patterning ofthe photoresist material; forming an organic light emitting layer bydripping ink that includes organic light emitting material into each ofthe plurality of openings and drying the ink; and forming a plurality ofsecond electrodes above the organic light emitting layer, wherein theplurality of openings include a peripheral opening located in aperipheral region of the array, the plurality of banks includes a firstbank and a second bank that each border the peripheral opening, thefirst bank being closer to a periphery of the array than the secondbank, the second bank being closer to a center of the array than thefirst bank, and when forming the plurality of openings and the pluralityof banks, the first bank and the second bank are formed such that aninclination angle of an innermost sidewall of the first bank that isadjacent the peripheral opening is greater than an inclination angle ofan outermost sidewall of the second bank that is adjacent the peripheralopening.
 8. The manufacturing method of claim 7, wherein the pluralityof openings includes a central opening that is located in a centralregion of the array, the plurality of banks includes a third bank and afourth bank that each border the central opening, the third bank beingcloser to the periphery of the array than the fourth bank, and thefourth bank being closer to the center of the array than the third bank,and when forming the plurality of openings and the plurality of banks,the third bank and the fourth bank are formed so that an inclinationangle of a innermost sidewall of the third bank that is adjacent thecentral opening is approximately equal to an inclination angle of anoutermost sidewall of the fourth bank that is adjacent the centralopening.
 9. The manufacturing method of claim 7, wherein, when formingthe organic light emitting layer, a first pinning location of the of theink dripped into the peripheral opening is set on the innermost sidewallof the first bank higher than a second pinning location of the of theink dripped into the peripheral opening set on the outermost sidewall ofthe second bank so that the organic light emitting layer has uniformfilm thickness after the ink is dried.
 10. The manufacturing method ofclaim 7, wherein, when forming the plurality of openings and theplurality of banks, the first bank and the second bank are formed suchthat the inclination angle of the innermost sidewall of the first bankis greater than the inclination angle of the outermost sidewall of thesecond bank by varying, during exposure of the photoresist material, afirst exposure amount of the photoresist material in a first sectioncorresponding to the innermost sidewall of the first bank from a secondexposure amount of the photoresist material in a second sectioncorresponding to the outermost sidewall of the second bank.
 11. Themanufacturing method of claim 10, wherein the first exposure amount inthe first section corresponding to the innermost sidewall of the firstbank is greater than the second exposure amount in the sectioncorresponding to the outermost sidewall of the second bank.
 12. Themanufacturing method of claim 7, wherein, when forming the plurality ofopenings and the plurality of banks, the first bank and the second bankare formed such that the inclination angle of the innermost sidewall ofthe first bank is greater than the inclination angle of the outermostsidewall of the second bank by using, during exposure of the photoresistmaterial, a mask in which a first degree of transparency in a firstsection corresponding to the innermost sidewall of the first bank and asecond degree of transparency in a second section corresponding to theoutermost sidewall of the second bank differ.
 13. The manufacturingmethod of claim 12, wherein the first degree of transparency in thefirst section corresponding to the innermost sidewall of the first bankis greater than the second degree of transparency in the second sectioncorresponding to the outermost sidewall of the second bank.
 14. Themanufacturing method of claim 7, wherein, when forming the plurality ofopenings and the plurality of banks, the first bank and the second bankare formed such that the inclination angle of the innermost sidewall ofthe first bank is greater than the inclination angle of the outermostsidewall of the second bank by: exposing the photoresist material in afirst section corresponding to the innermost sidewall of the first bankand in a second section corresponding to the outermost sidewall of thesecond bank; and additionally exposing the photoresist material in oneof the first section and the second section after exposing thephotoresist material in the first section and the second section. 15.The manufacturing method of claim 14, wherein the first sectioncorresponding to the innermost sidewall of the first bank isadditionally exposed.